Acetoacetate functional polysiloxanes

ABSTRACT

Functional polysiloxanes and curable coating compositions containing such polysiloxanes are disclosed. The curable compositions are useful in coatings where they provide excellent appearance, pot-life, humidity resistance and improved adhesion to galvanized steel substrates. A method for preparing the functional polysiloxanes is also disclosed.

This is a division of application Ser. No. 08/904,596, filed Aug. 1,1997, U.S. Pat. No. 5,952,443.

BACKGROUND OF THE INVENTION

Polysiloxane polyols are well known in the art. Japanese PatentPublication 48-19941 describes polysiloxane polyols which are obtainedby the dehydrogenation reaction between a polysiloxane hydride and analiphatic polyhydric alcohol or polyoxyalkylene alcohol to introduce thealcoholic hydroxy groups onto the polysiloxane backbone. In practice,however, it is difficult to obtain an industrially significant yield ofsuch polysiloxane polyols because such a dehydrogenation reactionreadily gels. Another problem encountered with this dehydrogenationreaction is the difficulty in obtaining a solvent capable of dissolvingboth reactants. Strongly hydrophilic alcohols such as polyglycerols arehighly soluble in alcohols and water, but insoluble in hydrocarbonsolvents. Polysiloxanes, however, are generally only soluble inhydrocarbon solvents such as toluene or n-hexane.

U.S. Pat. No. 4,431,789 to Okszaki et al. discloses a polysiloxanepolyol which is obtained by the hydrosilylation reaction between apolysiloxane containing silicon hydride and a polyglycerol compoundhaving an aliphatically unsaturated linkage in the molecule. Examples ofsuch polyglycerol compounds are those obtained by the reaction of allylalcohol and glycidol or by the reaction of diglycerin and allyl glycidylether. This reaction, a so-called hydrosilylation reaction, is theaddition reaction between an organosilicon compound having a hydrogenatom directly bonded to the silicon atom, i.e., a polysiloxane hydride,and an organic compound having aliphatic unsaturation in the moleculecarried out in the presence of a catalytic amount of a Group VIII noblemetal. The hydrosilylation reaction can proceed readily in the presenceof an alcoholic solvent which can dissolve both reactants. The resultingpolysiloxane polyols are useful as non-ionic surface active agents.

U.S. Pat. No. 5,260,469 discloses butoxylated polysiloxane polyols whichare disclosed as being useful in cosmetics.

Also known in the art are acetoacetate functional acrylic crosslinkingpolymers. U.S. Pat. No. 4,408,018 to Bartman et al. describes theintroduction of pendant acetoacetate functional moieties onto an acrylicpolymer backbone for crosslinking with alpha, beta-unsaturated estersvia the Michael addition reaction. The acetoacetate functional acrylicpolymers may be prepared in either of two ways. An acetoacetic ester ofa hydroxyl group containing acrylic monomer, such as hydroxyethylmethacrylate or hydroxyethyl acrylate, can be produced by thetransacetylation of the hydroxyl containing acrylic monomer with anacetoacetate. These acetylated monomers can then be copolymerized withother polymerizable monomers to introduce the acetoacetate moiety intothe acrylic polymer chain. Alternatively, an acrylic polymer chainhaving hydroxyl functionality thereon can be transesterified with analkyl acetoacetate to introduce the acetoacetate moiety into the acrylicpolymer backbone. The references also disclose the acetoacetylation ofthe hydroxyl groups of a polyester polyol to yield an acetoacetatecontaining polyester.

SUMMARY OF THE INVENTION

The present invention relates to novel functional polysiloxanes and amethod for the preparation of such polysiloxanes. Also disclosed is acurable coating composition containing the functional polysiloxanes.

The curable coating composition containing the functional polysiloxaneis readily curable at ambient temperatures and produces a cured filmwith excellent performance properties such as cure speed, low VOC,excellent humidity resistance, flexibility and adhesion over galvanizedsteel.

The functional polysiloxane having the general structural formula:##STR1## wherein the group represented by R^(a) contains a group havingthe general structure: ##STR2##

where the R groups are selected from the group consisting of OH andmonovalent hydrocarbon groups connected to the silicon atoms, m is atleast one; m' is 0 to 50, and n is 0 to 50. Preferably, the group R^(a)contains a group having the general structure: ##STR3## where X is N, Oor S.

The preparation of the functional polysiloxane of structural formula (I)comprises:

(a) hydrosilylating a polysiloxane containing silicon hydride, where theratio of hydrosilylated silicon atoms to non-hydrosilylated siliconatoms is at least 0.1:1, and preferably 0.1 to 10:1, with an alcohol,primary or secondary amine, or thiol containing vinyl or vinylidenegroups which are capable of hydrosilylating said polysiloxane containingsilicon hydride, to yield a polysiloxane containing hydroxyl, amine orthiol groups or mixtures thereof; and

(b) esterifying the hydrosilylated reaction product of (a) with theacetoacetate to produce the acetoacetate functional polysiloxane.

The curable coating composition comprises:

(a) a functional polysiloxane having the general formula (II) or (III)wherein at least one of the groups represented by R^(a) contains a grouphaving the general structural formula (I) or (IV), where n is 0 to 50; mis at least one; m' is 0 to 50; and in the case of structural formula(I), X is --N, O or S; and the other R groups are selected from thegroup consisting of OH and monovalent hydrocarbon groups bonded to thesilicon atoms; and

(b) a polyamine or a blocked polyamine.

In the preferred embodiment of the invention, X is O. Optionally, thecurable coating composition of the invention further comprises apolyacrylate curing agent.

The coated substrates have thereon a film comprising the cured reactionproduct of the following reactants:

(a) a functional polysiloxane having general structural formula (II) or(III) wherein at least one R^(a) group contains a group represented bythe structural formula (I) or (IV), where n is 0 to 50; m is at leastone; m' is 0 to 50; and in the case of structural formula (I), X is --N,O or S; and the R groups are selected from the group consisting of H, OHand monovalent hydrocarbon groups; and

(b) a polyamine or a blocked polyamine.

In the preferred embodiment of the invention, X is O. Optionally, thecoated substrate may have a film thereon further comprising as one ofthe reactants a polyacrylate curing agent.

DETAILED DESCRIPTION OF THE INVENTION

The functional polysiloxane of the present invention has the generalformula (II) or (III) wherein at least one of the groups represented byR^(a) contains a group having the general structure (I) or (IV) and inthe case of (I) where X is --N, O or S, preferably O; the R groups areselected from the group consisting of OH and monovalent hydrocarbongroups bonded to the silicon atoms; and m is at least one; m' is 0 to50; n is 0 to 50, preferably 0 to 35, and more preferably 2 to 15. Bymonovalent hydrocarbon groups is meant organic groups containingessentially carbon and hydrogen. The hydrocarbon groups may bealiphatic, aromatic, cyclic or acyclic and may contain from 1 to 24 (inthe case of aromatic from 3 to 24) carbon atoms. Optionally, thehydrocarbon groups may be substituted with heteroatoms, typicallyoxygen. Examples of such monovalent hydrocarbon groups are alkyl,alkoxy, aryl, alkaryl or alkoxyaryl groups.

Preferably the functional polysiloxane has an equivalent weight of 100to 1500, more preferably from 150 to 500 (grams/equivalent) based uponthe equivalents of acetoacetate.

At least one of the groups represented by R^(a) typically contains agroup of the following general structure: ##STR4## where L is an organiclinking group and x is 1 to 3. Preferably L is alkylene, oxyalkylene oralkylene aryl. By alkylene is meant acyclic or cyclic alkylene groupshaving a carbon chain length of from C₂ to C₂₅. Examples of suitablealkylene groups are those derived from propene, butene, pentene,1-decene, isoprene, myrcene and 1-heneicosene. By oxyalkylene is meantan alkylene group containing at least one ether oxygen atom and having acarbon chain length of from C₁ to C₂₅, preferably of from C₂ to C₄.Examples of suitable oxyalkylene groups are those associated withtrimethylolpropane monoallylether, trimethylolpropane diallylether andethoxylated allylether. By alkylene aryl is meant an acyclic alkylenegroup containing at least one aryl group, preferably phenyl, and havingan alkylene carbon chain length of from C₂ to C₂₅. The aryl group mayoptionally be substituted. Suitable substituent groups may includehydroxyl, benzyl, carboxylic acid and aliphatic groups. Examples ofsuitable alkylene aryl groups include styrene and 3-isopropenyl-α,α-dimethylbenzyl isocyanate.

Preferably the functional polysiloxane of the present invention is anacetoacetate functional polysiloxane and has the following generalstructural formula: ##STR5## where m is at least one; m' is 0 to 50; nis 0 to 50; R is selected from the group consisting of OH and monovalenthydrocarbon groups connected to the silicon atoms; and at least aportion of R^(b) groups has the following structure: ##STR6## wherein R₁is alkylene, oxyalkylene or alkylene aryl; and R₂ is alkylene,oxyalkylene or alkylene aryl, and z is one to 3 and where Y is selectedfrom the group consisting of alkyl, Cl, Br, I and OR', preferably whereR' is C₁ to C₁₂ alkyl. When only a portion of the hydroxyl groups of thepolysiloxane polyol produced in the hydrosilylation step are esterified,the remaining R^(b) groups are:

L--OH and/or R₁ --O--R₂ --OH where L, R₁ and R₂ are as defined above.

Preferably, the ratio of m:n in the acetoacetate functional polysiloxaneof structure (IV) is at least 0.1: 1, preferably 0.1 to 10: 1. Ratiosless than 0.1 to 1 are not preferred because these materials aretypically not compatible with organic materials (i.e., resins andsolvents).

A method of preparing the acetoacetate functional polysiloxane of thepresent invention comprises

(a) hydrosilylating a polysiloxane containing silicon hydride such asone having the structure: ##STR7## wherein the R groups are selectedfrom the group consisting of OH and monovalent hydrocarbon groupsconnected to the silicon atoms; n is 0 to 50; m is at least one; and m'is 0 to 50, such that the ratio of hydrogen-bonded silicon atoms tonon-hydrogen-bonded silicon atoms is at least 0.1: 1, preferably from0.1 to 10:1; with an alcohol, primary or secondary amine, or thiolcontaining vinyl or vinylidene groups which are capable ofhydrosilylating said polysiloxane containing silicon hydride, to producea polysiloxane containing hydroxyl, amine or thiol groups or mixturesthereof; and

(b) esterifying the hydrosilylated reaction product of (a) with anacetoacetate such as one having the structure: ##STR8## where Y' isselected from the group consisting of Cl, Br, I and OR', preferably OR',where R' is C₁ to C₁₂ alkyl, to produce an acetoacetate functionalpolysiloxane.

Alternatively, the esterification can be conducted with the alcoholbefore the hydrosilylation step.

Preferably n is from about 0 to 50, more preferably from about 0 to 35,and even more preferably from 2 to 15. Examples of the polysiloxanecontaining silicon hydride are 1,1,3,3-tetramethyl disiloxane andpolysiloxane containing silicon hydrides where n is 4 to 5, commerciallyavailable from PPG Industries, Inc. as MASILWAX BASE.

It is preferred that the polysiloxane containing silicon hydride ishydrosilylated with an alkenyl alcohol, preferably an allylicpolyoxyalkylene alcohol. Examples of suitable alkenyl alcohols areallylic polyoxyalkylene alcohols and include polyethoxylated allylicalcohol, trimethylolpropane monoallylether and polypropoxylated allylalcohol. In the most preferred embodiment of the invention, the alkenylalcohol is trimethylolpropane monoallylether.

Typically the preparation of the acetoacetate functional polysiloxane iscarried out in two steps: (1) a hydrosilylation step and (2) anesterification step. In step 1, the alcohol, primary or secondary amine,or thiol is added at ambient temperature to a reaction vessel equippedwith a means for maintaining a nitrogen blanket. Added concurrently isabout from 20 to 75 ppm sodium bicarbonate or metal acetate salt toinhibit the possible undesirable side reactions such as those associatedwith acetal condensation via a propenyl ether moiety. The temperature isincreased to 75° C. under a nitrogen blanket at which time about 5% ofthe polysiloxane containing silicon hydride is added under agitation. Acatalyst such as a transition metal, for example, nickel, nickelcompounds and iridium salts, preferably chloroplatinic acid, is thenadded and the reaction is permitted to exotherm to 95° C. Addition ofthe remaining portion of the polysiloxane containing silicon hydride iscompleted as the reaction temperature is maintained at 80-85° C. Thereaction is monitored by infrared spectroscopy for disappearance of thesilicon hydride absorption band (Si--H: 2150 cm⁻¹).

To this product is added the acetoacetate and the temperature isincreased to 120° C. under a nitrogen sparge. During heating, theevolving alcohol is collected. Complete distillation provides theacetoacetate functional polysiloxane of the present invention.

The curable coating composition of the present invention comprises (a) afunctional polysiloxane of the structural formula (II) or (III) whereinat least one of the groups represented by R^(a) contains a group havingthe general structural formula (IV) or (I), where n, m, m', R and X areas defined above for formulae (II) and (III); and (b) a polyarnine orblocked polyarnine. Preferably the functional polysiloxane has thegeneral structural formula (VII) or (VIII) where n, m, m', z, R₁, R₂,R_(b) and Y are all as defined above for formula (VI), (VII), (VIII) and(IX).

Preferably, the blocked polyamine is a polyketimine having thestructure: ##STR9## where p is 0 to 6; R₃ and R₄ are the same ordifferent and are alkylene, oxyalkylene, or alkylene aryl; and the R₅and the R₅ groups are independently H or alkyl containing from 2 to 20carbon atoms, preferably 2 to 6 carbon atoms; or aryl containing from 6to 24 carbon atoms; are each substantially inert to the ketimineformation reaction; and R₅ and R₅ together can form part of a 3,4,5, or6 membered ring.

Besides ketimines, aldemines can also be used and unless otherwiseindicated, ketimines and polyketimines is meant to include aldemines andpolyaldemines. Preferably the polyketimine is the reaction product of apolyepoxide with a ketimine containing secondary amine group. Thepolyepoxide can be selected from materials which contain at least twooxirane groups in the molecule. An oxirane group may be represented bythe general structural formula: ##STR10## where q is at least two; R₇ isH or CH₃ ; and R₈ broadly represents an organic based molecule orpolymer typically composed of carbon, hydrogen, oxygen, and optionallynitrogen and/or sulfur. Hydroxyl substituent groups can also be presentand frequently are, as well as halogen and ether groups. Generally theepoxide equivalent weight ranges from about 100 to about 1000,preferably from about 100 to about 500, and more preferably from about150 to about 250. These polyepoxides can be broadly categorized as beingaliphatic, aromatic, cyclic, acyclic, alicyclic or heterocyclic.

One particularly preferred group of polyepoxides for use in the presentinvention are the epoxy novalac resins which are prepared by reacting anepihalohydrin with the condensation product of an aldehyde with amonohydric or polyhydric phenol. One example is the reaction product ofepichlorohydrin with a phenolformaldehyde condensate.

Another particularly preferred group of polyepoxides are thepolyglycidyl ethers of polyhydric aromatic alcohols, which are preparedby reacting an epihalohydrin, such as epichlorohydrin, with a polyhydricaromatic alcohol. Suitable examples of dihydric phenols includeresorcinol, catechol, hydroquinone, bis(4-hydroxyphenyl)-1,1-isobutane;4,4-dihydroxybenzophenone; bis(4-hydroxyphenyl)-1,1-ethane;bis(2-hydroxynaphenyl)methane; 1,5-hydroxynaphthalene and4,4'-isopropylidenediphenol, i.e., Bisphenol A. Bisphenol A ispreferred.

It should be understood that mixtures of polyepoxides may also beutilized in the present invention.

A specific example of a polyepoxide-ketimine reaction product involvesreacting a polyamine such as one mole of diethylenetriamine with twomoles of methylisobutyl ketone to produce a diketimine with secondaryamine functionality. Alternatively, an aldehyde such as isobutylaldehydeor benzaldehyde can be used in place of or in conjunction with theketone to form an aldimine. This ketimine, or aldimine, is then reactedwith a polyepoxide, depleting effectively all of the oxirane groups ofthe polyepoxide and resulting in a ketimine or aldimine which isessentially free of all oxirane groups. By "essentially free of oxiranegroups" is meant that the epoxy equivalent weight of the reactionproduct is measured to be about at least 5000 (grams/equivalents), onaverage the reaction product contains less than 1, more preferably, onaverage, less than 0.5 oxirane groups per molecule.

Representative of the polyamines which may be utilized in the presentinvention are aliphatic or cycloaliphatic amines having from 2 to 200carbon atoms and from 2 to 10 primary and/or secondary amino groups,preferably from 2 to 4 primary amino groups. Examples of suitablepolyamines include ethylenediamine, propylenediamine, butylenediamine,pentamethylenediamine, hexamethylenediamine; decamethylenediamine;4,7-dioxadecane-1,10-diamine; dodecamethylenediamine;4,9-dioxadodecane-1,12-diamine;7-methyl-4,10-dioxatridecane-1,13-diamine; 1,2-diaminocyclohexane;1,4-diaminocyclohexane; 4,4'-diaminodicyclohexyl methane; isophoronediamine; bis(3-methyl-4-aminocyclohexyl)methane;2,2-bis(4-aminocyclohexyl)propane; nitrile tris(ethane amine);bis(3-aminopropyl) methylamine; 2-amino-1-(methylamino)propane;3-amino-1-(cyclohexylamino)propane; and N-(2-hydroxyethyl)ethylenediamine.

A particularly preferred group of polyamines that are useful in thepractice of the present invention can be represented by the followingstructural formula:

    H.sub.2 N--(--R.sub.3 --NH).sub.p --R.sub.4 --NH.sub.2     (XV)

where the R₃ and R₄ can be the same or different and represent analkylene, oxyalkylene or alkylene aryl group containing from 2 to 20 andpreferably from 2 to 10 carbon atoms and p is from about 1 to 6,preferably from about 1 to 3. Nonlimiting examples of polyalkylenepolyamines suitable for use in the present invention includediethylenetriamine, dipropylenetriamine and dibutylenetriamine.

The aldehyde or ketone which is reacted with the polyamine can berepresented by the following structural formula: ##STR11## wherein R₅and R'₅ are independently H, C₂ to C₂₀ alkyl or C₆ to C₂₄ aryl, and R₅and R'₅ together can form part of a 3, 4, 5, or 6 membered ring.Examples of suitable aldehydes and ketones for use in the presentinvention as modifiers or blocking agents for the amine groups include,acetone, diethyl ketone, methylisobutyl ketone, diisobutyl ketone,isobutyraldehyde, hydroxybutyraldehyde, benzaldehyde, salicylaldehyde,pentanone, cyclohexanone, methylamyl ketone, ethylamyl ketone,hydroxycitronellal, isophorone and decanone. Ketones preferred for usein the present invention include acetone, diethyl ketone, diisobutylketone, pentanone, cyclohexanone, methylarnyl ketone, isophorone,decanone and methylisobutyl ketone and methylphenyl ketone.

In one preferred embodiment of the present invention, the polyketimineis essentially free of oxirane functionality; has an average of at leasttwo ketimine groups per molecule, preferably an average of about from 2to about 25 ketimine groups per molecule, and more preferably of fromabout 3 to about 6 ketimine groups per molecule; and has a weightaverage molecular weight of from about 1000 to 50,000, preferably offrom about 1000 to about 10,000, and more preferably of from about 1000to about 5000, as determined by gel permeation chromatography (GPC)using a polystyrene standard.

Polyamines can also be used as component (b) in the curable composition.Examples of such polyarnines are those described above.

Optionally, the curable coating composition of the present invention cancontain a polyacrylate functional component. The preferred polyacrylatefunctional component contains at least two acryloyl groups ormethacryloyl groups per molecule. Suitable polyacrylate functionalcomponents include the esterification or transesterification reactionproducts of acrylate or methacrylate containing materials, such asacrylic or methacrylic acids or acrylic or methacrylic esters asdescribed in more detail below, with di-, tri- or polyvalent polyols,including polyester polyols and polyether polyols; and the reactionproduct of a hydroxyl group containing acrylate or methacrylate with apolyisocyanate.

The polyol used in the transesterification reaction is typically a lowmolecular weight diol, triol or tetrol. These polyols generally have aformula molecular weight ranging from about 50 to about 1000, andpreferably from about 100 to about 500. Examples of suitable polyolsinclude ethylene glycol, propylene glycol, diethylene glycol,tetramethylene diol, neopentyl glycol, hexamethylene diol,1,6-hexanediol, cyclohexane diol, bis-(4-hydroxycyclohexyl) methane,glycerol, trimethylolethane, trimethylolpropane,tris(2-hydroxyethyl)-isocyanurate, pentaerythritol and ethoxylatedBisphenol A. Preferably a diol such as ethoxylated Bisphenol is used. Itshould be understood, however, that if desired, higher molecular weightpolyols such as oligomeric or polymeric polyols can be utilized toprepare the polyacrylate containing material.

As aforementioned, the polyacrylate functional material may also be thereaction product of a polyisocyanate and a hydroxyl group containingacrylate or methacrylate. The polyisocyanate is typically a lowmolecular weight diisocyanate or triisocyanate having a formula weightof from about 200 to 1000, and preferably from about 200 to 600.Examples of suitable polyisocyanate materials includetoluenediisocyanate, 4,4'-diphenylmethanediisocyanate,isophoronediisocyanate, tris(toluenediisocyanate)trimethylolpropane,1,6-hexamethylenediisocyanate, 1,4-tetramethylenediisocyanate and4,4'-methylenebis(cyclohexyl isocyanate). It should be understood,however, that if desired, higher molecular weight polyisocyanates, suchas oligomeric or polymeric materials can be utilized to prepare thepolyacrylate functional material.

The acrylate or methacrylate containing material, which is reactedeither with the above-mentioned polyol or polyisocyanate to produce thepolyacrylate functional material, can be represented by the generalstructural formula: ##STR12## where R₉ is H or CH₃, and R₁₀ is H, alkylcontaining from one to 20 carbons, or hydroxy alkyl containing from 1 to20 carbons. Nonlimiting examples of suitable acrylate or methacrylatecontaining materials include acrylic acid, methacrylic acid, methylmethacrylate, ethyl methacrylate, butyl methacrylate, hexylmethacrylate, 2-hydroxyethyl methacrylate, methyl acrylate, ethylacrylate, butyl acrylate, hexyl acrylate and 2-hydroxyethyl acrylate.

The polyacrylate functional materials used in the present inventiongenerally have a weight average molecular weight of from about 100 toabout 50,000 as determined by GPC using a polystyrene standard. In thepreferred embodiment of the present invention, the polyacrylatefunctional materials are low molecular weight materials which have aformula weight generally from about 100 to about 5000, and morepreferably from about 100 to about 500.

Examples of suitable polyacrylate functional materials include1,6-hexanediol diacrylate, trimethylolpropane triacrylate,pentaerythritol tetraacrylate, ethoxylated bisphenol A diacrylate andtris(2-hydroxyethyl)isocyanurate triacrylate.

Although not intending to be bound by any theory, it is believed thatthe functional polysiloxane and the polyacrylate functional material, ifpresent, react with the polyketimine to cure the claimed coatingcompositions. The reaction is believed to proceed by the deblocking ofketones from the polyketimine which exposes the primary amines which arebelieved to subsequently react with the acetoacetate functionalpolysiloxane and, if present, the polyacrylate functional material.

Optionally, an effective amount of acid catalyst can be used toaccelerate the cure. Examples of appropriate acid catalysts includestearic acid, isostearic acid, undecylenic acid and phosphoric acid. Itshould be understood that any organic or inorganic acid could serve as acatalyst, but it is preferred that the acid be monofunctional. If used,the acid is generally present in minor amounts, typically from about 0.1to about 1.0 percent by weight, the percentage based on total weight ofresin solids.

It is preferred that the curable coating composition of the presentinvention be essentially free of strong base. By "strong base" is meantthat the pK_(b) of the base is greater than or equal to 11. By"essentially free of strong base" is meant that no more than 1 percentby weight, the percentage based on total weight of resin solids, ispresent in the composition. The presence of a strong base is believed tocatalyze Michael addition between the acetoacetate functionalpolysiloxane and, if present in the composition, the polyacrylatefunctional material. (See Clemens et al., "A Comparison of Catalysts forCrosslinking Acetoacetylated Resins via the Michael Reaction", Journalof Coatings Technology, Vol. 61, No. 770, March 1989) Cure by thisMichael reaction is not desirable since it has been observed to resultin unacceptably reduced pot-life of the coating composition.

The curable coating compositions of the invention can be pigmented orunpigmented. Suitable pigments for color coats include opaque,transparent and translucent pigments generally known for use in coatingapplications. Examples include titanium dioxide, zinc oxide, antimonyoxide, iron oxide, carbon black and phthalocyanine blue. Metallicpigments such as aluminum flake and metal oxide-coated micas can also beused. The coatings may also contain extender pigments such as calciumcarbonate, clay, silica, talc, etc. When pigment is used, it typicallypresent in the composition in amounts such that the pigment to binderratio is from about 0.03 to 6.0:1.

In addition to the foregoing components, the coating compositions of theinvention may include one or more optional ingredients such asplasticizers, anti-oxidants, light stabilizers, mildewcides andfungicides, surfactants and flow control additives or catalysts as arewell known in the art.

The components present in the curable coating composition of the presentinvention generally are dissolved or dispersed in an organic solvent.Organic solvents which may be used include, for example, alcohols,ketones, aromatic hydrocarbons, esters or mixtures thereof. Specificexamples include ethanol, acetone, methyl ethyl ketone, methyl amylketone, xylenes and butyl acetate. Typically, organic solvent is presentin amounts of 5 to 80 percent by weight based on total weight of thecomposition.

The coating compositions of the invention are particularly useful astopcoats and particularly as primers. Because of their low temperaturecuring properties, they are particularly suitable for use in automotiverefinish applications. Once the functional polysiloxane component andthe polyamine or blocked polyamine component come into contact with eachother, the coating composition will begin to cure at ambient conditions.Accordingly, it is desirable to prepare the compositions in the form ofa two-package system with the polyamine or blocked polyamine componentin one package and the functional polysiloxane component and,optionally, the polyacrylate functional material in a second package.

The functional polysiloxane is generally present in the curable coatingcomposition of the present invention in amounts of 5 to about 65, andpreferably from about 10 to about 25 percent by weight based on totalweight of resin solids. The polyamine or blocked polyamine is generallypresent in amounts of from 25 to about 65, and preferably from about 35to about 55 percent by weight based on total weight of resin solids. Theoptional polyacrylate functional material can be present in amounts upto 15, and preferably from about 2.5 to about 7.5 percent by weightbased on total weight of resin solids.

The coating composition of the invention can be applied to the substrateby any conventional method such as brushing, dipping, flow coating, rollcoating and spraying. Typically, they are most often applied byspraying. The compositions can be applied over a wide variety of primedand unprimed substrates such as wood, metal, glass, cloth, plastics,leather, foams and the like. Although the compositions can be cured atambient temperatures, they can be cured at elevated temperatures tohasten the cure. An example would be forced air curing in a down draftbooth at about 40° to 60° C. which is common in the automotive refinishindustry.

The compositions of the invention in the pigmented form can be applieddirectly to a substrate to form a color coat. The color coat may be inthe form of a primer for subsequent application of a top coat or may bea colored top coat. When used as a primer coating, thicknesses of 0.4 to4.0 mils are typical. When used as a color top coat, coating thicknessesof about 0.5 to 4.0 mils are usual.

In applying composite coatings using the coating composition of thepresent invention, the initially applied coating can be cured prior tothe application of the second coat. Alternatively, the coating can beapplied by a wet-on-wet technique in which the second coating is appliedto the first coating (usually after a flash time at room temperature orslightly elevated temperature to remove solvent or diluent, butinsufficient time to cure the coating) and the two coatings are co-curedin a single step.

Only one of the coatings in the composite coating needs to be based onthe coating composition of the present invention. The other coatingcomposition can be based on a film-forming system containing athermoplastic and/or thermosetting film-forming resin well known in theart such as cellulosics, acrylics, polyurethanes, polyesters includingalkyds, aminoplasts, epoxies and mixtures thereof. These film-formingresins are typically formulated with various other coatings ingredientssuch as pigments, solvents and optional ingredients mentioned above.

The curable coating compositions of the present invention areparticularly useful as primer surfacer coating compositions forautomotive refinish applications. The compositions can be applied by anyof the foregoing means of application directly to bare metal surfacesand, after being allowed to dry and the finish prepared such as bysanding, coated directly with a color top coat or a color-clearcomposite coating. The claimed coating compositions can be used as asingle primer or undercoat beneath a top coat replacing separateundercoats which have historically been required to obtain optimumresults.

The following examples illustrate the invention and should not beconstrued as a limitation on the scope thereof. Unless specificallyindicated otherwise, all percentages and amounts are by weight.

EXAMPLE 1

This example describes the preparation of a disiloxane tetrol, a productof the hydrosilylation step in the preparation of the acetoacetatefunctional polysiloxane of the present invention. The disiloxane tetrolwas prepared from the following mixture of ingredients:

    ______________________________________                                                    Equivalent          Parts By Weight                                 Ingredients Weight Equivalents (grams)                                      ______________________________________                                        Charge I:                                                                       Trimethylolpropane 174.0 7.7 1335.7                                           monoallylether                                                                Charge II:                                                                    1,1,3,3-tetramethyldi- 67.0 7.7  515.2                                        siloxane                                                                      Charge III:                                                                   Chloroplatinic acid   10 ppm                                                ______________________________________                                    

To a suitable reaction vessel equipped with a means for maintaining anitrogen blanket, Charge I and an amount of sodium bicarbonateequivalent to 20 to 25 ppm of total monomer solids were added at ambientconditions and the temperature was gradually increased to 75° C. under anitrogen blanket. At that temperature, about 5.0% of Charge II was addedunder agitation, followed by the addition of Charge III, equivalent to10 ppm of active platinum based on total monomer solids. The reactionwas then allowed to exotherm to 95° C. at which time the remainder ofCharge II was added at a rate such that the temperature did not exceed95° C. After completion of this addition, the reaction temperature wasmaintained at 95° C. and monitored by infrared spectroscopy fordisappearance of the silicon hydride absorption band (Si--H, 2150 cm⁻¹).

EXAMPLE 2

This example describes the preparation of a polysiloxane tetrol, aproduct of the hydrosilylation of MASILWAX BASE siloxane with anapproximate degree of polymerization of 3 to 4, i.e., (SiO)₃ to (SiO)₄.The siloxane tetrol was prepared from the following mixture ofingredients:

    ______________________________________                                                    Equivalent          Parts By Weight                                 Ingredients Weight Equivalents (grams)                                      ______________________________________                                        Charge I:                                                                       Trimethylolpropane 174.0 9.4 1630.0                                           monoallylether                                                                Charge II:                                                                    MASILWAX BASE.sup.1 156.7 9.4 1467.4                                          Charge III:                                                                   Chloroplatinic acid   10 ppm                                                ______________________________________                                         .sup.1 Polysiloxane containing silicon hydride, commercially available        from PPG Industries, Inc.                                                

To a suitable reaction vessel equipped with a means for maintaining anitrogen blanket, Charge I and an amount of sodium carbonate equivalentto 20 to 25 ppm of total monomer solids were added at ambient conditionsand the temperature was gradually increased to 75° C. under a nitrogenblanket. At that temperature, about 5.0% of Charge II was added underagitation, followed by the addition of Charge III, equivalent to 10 ppmof active platinum based on total monomer solids. The reaction was thenallowed to exotherm to 95° C. at which time the remainder of Charge IIwas added at a rate such that the temperature did not exceed 95° C.After completion of this addition, the reaction temperature wasmaintained at 95° C. and monitored by infrared spectroscopy fordisappearance of the silicon hydride absorption band (Si--H, 2150 cm⁻¹).

EXAMPLE 3

This example describes the preparation of a disiloxane propoxyldiol, aproduct of the hydrosilylation step of tetramethyl disiloxane. Thedisiloxane propoxyldiol was prepared from the following mixture ofingredients:

    ______________________________________                                                    Equivalent          Parts By Weight                                 Ingredients Weight Equivalents (grams)                                      ______________________________________                                        Charge I:                                                                       Allyl Propoxylate.sup.1 150.8 3.0 452.4                                       Charge II:                                                                    Tetramethyldisiloxane 67.0 3.0 201.0                                          Charge III:                                                                   Chloroplatinic acid   10 ppm                                                ______________________________________                                         .sup.1 Commercially available as ARCAL AP1375 from ARCO Chemical Company.

To a suitable reaction vessel equipped with a means for maintaining anitrogen blanket, Charge I and an amount of sodium bicarbonateequivalent to 20 to 25 ppm of total monomer solids were added at ambientconditions and the temperature was gradually increased to 75° C. under anitrogen blanket. At that temperature, about 5.0% of Charge II was addedunder agitation, followed by the addition of Charge III, equivalent to10 ppm of active platinum based on total monomer solids. The reactionwas then allowed to exotherm to 95° C. at which time the remainder ofCharge II was added at a rate such that the temperature did not exceed95° C. After completion of this addition, the reaction temperature wasmaintained at 95° C. and monitored by infrared spectroscopy fordisappearance of the silicon hydride absorption band (Si--H, 2150 cm⁻¹).

EXAMPLE 4

This example describes the preparation of a polysiloxane propoxyldiol, aproduct of the hydrosilylation of MASILWAX. The polysiloxanepropoxyldiol was prepared from the following mixture of ingredients:

    ______________________________________                                                    Equivalent          Parts By Weight                                 Ingredients Weight Equivalents (grams)                                      ______________________________________                                        Charge I:                                                                       Allyl Propoxylate.sup.1 150.8 3.0 452.4                                       Charge II                                                                     MASILWAX BASE.sup.2 156.7 3.0 468.0                                           Charge III:                                                                   Chloroplatinic acid   10 ppm                                                ______________________________________                                         .sup.1 Commercially available as ARCAL AP1375 from ARCO Chemical Company.     .sup.2 Polysiloxanecontaining silicon hydride, commercially available fro     PPG Industries, Inc.                                                     

To a suitable reaction vessel equipped with a means for maintaining anitrogen blanket, Charge I and an amount of sodium bicarbonateequivalent to 20 to 25 ppm of total monomer solids were added at ambientconditions and the temperature was gradually increased to 75° C. under anitrogen blanket. At that temperature, about 5.0% of Charge II was addedunder agitation, followed by the addition of Charge III, equivalent to10 ppm of active platinum based on total monomer solids. The reactionwas then allowed to exotherm to 95° C. at which time the remainder ofCharge II was added at a rate such that the temperature did not exceed95° C. After completion of this addition, the reaction temperature wasmaintained at 95° C. and monitored by infrared spectroscopy fordisappearance of the silicon hydride absorption band (Si--H, 2150 cm⁻¹).

EXAMPLE 5

This example describes the preparation of a styrenated polysiloxanepolyol, a product of the hydrosilylation of a polysiloxane with anapproximate degree of polymerization of 34, i.e., (Si--O)₃₄. Thepolysiloxane polyol was prepared from the following mixture ofingredients:

    ______________________________________                                                    Equivalent          Parts By Weight                                 Ingredients Weight Equivalents (grams)                                      ______________________________________                                        Charge I:                                                                       Alpha-methylstyrene 118.0 2.3 272.9                                           Polysiloxane 162.2 3.1 501.5                                                  (Si--O).sub.34.sup.1                                                          Charge II:                                                                    Trimethylolpropane 174.0 .97 168.0                                            monoallylether                                                                Charge III:                                                                   Chloroplatinic acid   10 ppm                                                ______________________________________                                         .sup.1 Polysiloxane (Si--O).sub.34 containing silicon hydride.           

To a suitable reaction vessel equipped with a means for maintaining anitrogen blanket, Charge I was added at ambient conditions. Added to thereaction vessel was 135 microliters, 7.5% solution of chloroplatinicacid, equivalent to 10 ppm of active platinum based on total monomersolids. The temperature was gradually increased to 80° C. under anitrogen blanket. The reaction was then allowed to exotherm to 151° C.,then subsequently cooled back to 80° C., at which time Charge II wasadded. with 70 ppm of potassium acetate. The reaction was again allowedto exotherm to approximately 150° C. before cooling to and maintainingat 95° C. while monitoring by infrared spectroscopy for disappearance ofthe silicon hydride absorption band (Si--H, 2150 cm⁻¹).

EXAMPLE 6

This example describes the acetoacetylation of the disiloxane tetrol ofExample 1 to produce the acetoacetate functional polysiloxane of thepresent invention. The acetoacetate functional polysiloxane was preparedfrom the following mixture of ingredients:

    ______________________________________                                                    Equivalent          Parts By Weight                                 Ingredients Weight Equivalents (grams)                                      ______________________________________                                        Charge I                                                                        Disiloxane tetrol of 123.4 0.8 100.0                                          Example 1                                                                     Charge II                                                                     Tertiary 158.0 0.8 126.4                                                      butylacetoacetate                                                           ______________________________________                                    

To a suitable reaction vessel equipped with a means for a nitrogensparge were added Charge I and Charge II at ambient conditions. Thetemperature was gradually increased to 120° C. under a nitrogen sparge.During heating, the evolving tertiary butanol was collected andatmospheric distillation was continued for about one hour at 120° C. atwhich time the remaining t-butanol was removed by vacuum distillation(at 30 mm Hg). Completion of the distillation provided the acetoacetatefunctional polysiloxane of the present invention which was confirmed bythe OH value, volume of tertiary butanol collected and the disappearanceof OH as determined by IR analysis. Also, the structure can bedetermined by NMR and elemental analysis.

EXAMPLE 7

This example describes the acetoacetylation of the polysiloxane tetrolof Example 2 to produce the acetoacetate functional polysiloxane of thepresent invention. The acetoacetate functional polysiloxane was preparedfrom the following mixture of ingredients:

    ______________________________________                                                    Equivalent          Parts By Weight                                 Ingredients Weight Equivalents (grams)                                      ______________________________________                                        Charge I                                                                        Polysiloxane tetrol of 179.2 2.2 385.6                                        Example 2                                                                     Charge II                                                                     Tertiary 158.0 2.2 340.0                                                      butylacetoacetate                                                           ______________________________________                                    

To a suitable reaction vessel equipped with means for a nitrogen spargewere added Charge I and Charge II at ambient conditions. The temperaturewas gradually increased to 120° C. under a nitrogen sparge. Duringheating, the evolving tertiary butanol was collected and atmosphericdistillation was continued for about one hour at 120° C. at which timethe remaining t-butanol was removed by vacuum distillation (at 30 mmHg). Completion of the distillation provided the acetoacetate functionalpolysiloxane of the present invention which was confirmed by the methodsin Example 6.

EXAMPLE 8

This example describes the acetoacetylation of the polysiloxanepropoxyldiol of Example 4 to produce the acetoacetate functionalpolysiloxane of the present invention. The acetoacetate functionalpolysiloxane was prepared from the following mixture of ingredients:

    ______________________________________                                                    Equivalent          Parts By Weight                                 Ingredients Weight Equivalents (grams)                                      ______________________________________                                        Charge I                                                                        Polysiloxane propoxyl- 283.3 2.8 800.0                                        diol of Example 4                                                             Charge II                                                                     Tertiary 158.0 2.8 445.6                                                      butylacetoacetate                                                           ______________________________________                                    

To a suitable reaction vessel equipped with means for a nitrogen spargewere added Charge I and Charge II at ambient conditions. The temperaturewas gradually increased to 120° C. under a nitrogen sparge. Duringheating, the evolving tertiary butanol was collected and atmosphericdistillation was continued for about one hour at 120° C. at which timethe remaining t-butanol was removed by vacuum distillation (at 30 mmHg). Completion of the distillation provided the acetoacetate functionalpolysiloxane of the present invention which was confirmed by the methodsin Example 6.

EXAMPLE 9

This example describes the acetoacetylation of the styrenatedpolysiloxane polyol of Example 5 to produce the acetoacetate functionalpolysiloxane of the present invention. The acetoacetate functionalpolysiloxane was prepared from the following mixture of ingredients:

    ______________________________________                                                    Equivalent          Parts By Weight                                 Ingredients Weight Equivalents (grams)                                      ______________________________________                                        Charge I                                                                        Styrenated polysil- 485.3 0.649 315.0                                         oxane of Example 5                                                            Charge II                                                                     Tertiary 158.0 0.649 102.5                                                    butylacetoacetate                                                           ______________________________________                                    

To a suitable reaction vessel equipped with means for a nitrogen spargewere added Charge I and Charge II at ambient conditions. The temperaturewas gradually increased to 120° C. under a nitrogen sparge. Duringheating, the evolving tertiary butanol was collected and atmosphericdistillation was continued for about one hour at 120° C. at which timethe remaining t-butanol was removed by vacuum distillation (at 30 mmHg). Completion of the distillation provided the acetoacetate functionalpolysiloxane of the present invention which was confirmed by the methodsin Example 6.

EXAMPLE 10

This example describes the preparation of a two-component curable primercoating composition containing the acetoacetylated disiloxane tetrol ofExample 6. The pre-blended crosslinker component, which contains theacetoacetylated disiloxane tetrol, was combined under agitation with thepigmented component which is commercially available as NCP-270 from PPGIndustries, Inc. just prior to application to a metal substrate.

    ______________________________________                                                           Formula Weight                                                                            Solid Weight                                     INGREDIENT (grams) (grams)                                                  ______________________________________                                        PIGMENTED COMPONENT:                                                            methyl isobutyl ketone (MIBK) 26.3 --                                         butyl acetate 28.8 --                                                         xylene 16.7 --                                                                novalac ketimine resin (in MIBK).sup.1 42.7 35.2                              acrylic grind resin (in Butyl Acetate).sup.8 6.7 4.0                          Dysperbyk 110.sup.2 4.4 2.2                                                   MPA2000T polyethylene wax.sup.3 2.1 0.4                                       talc 77.9 77.9                                                                Bentone SD-2.sup.4 3.9 3.9                                                    Titanium dioxide 31.5 31.5                                                    barium sulfate 35.1 35.1                                                      silica .9 .9                                                                  zinc phosphate 32.3 32.3                                                      iron oxide 6.5 6.5                                                            carbon black 1.1 1.1                                                          butyl acetate 8.6 --                                                          ketimine resin (in MIBK).sup.7 26.3 24.5                                      Subtotal 351.8 255.5                                                          CROSSLINKER COMPONENT:                                                        acetone 6.7 --                                                                methyl amyl ketone 7.6 --                                                     xylene 7.1 --                                                                 siloxane acetoacetate of Example 6 51.9 51.9                                  epoxy silane.sup.5 5.0 5.0                                                    diacrylate resin.sup.6 5.0 5.0                                                isostearic acid .2 .2                                                         Subtotal 83.5 62.1                                                            Total 435.3 317.6                                                           ______________________________________                                         .sup.1 Reaction product of an epoxy novalac (EPN 1139) available from Cib     Geigy and the ketimine of diethylene triamine and methyl isobutyl ketone.     .sup.2 Wetting agent available from BYKChemie.                                .sup.3 Wax dispersion available from Rheox Inc.                               .sup.4 Antisettling agent available from Rheox Inc.                           .sup.5 Adhesion promoter available as A187 from OSi Specialties Inc.          .sup.6 Bisphenol A diacrylate available from Sartomer Corp.                   .sup.7 Ketimine of isophorone diamine and MIBK.                               .sup.8 Acrylic copolymer of styrene, diethyl aminoethyl methacrylate,         methyl methacrylate, hydroxyethyl methacrylate, 2ethylhexyl acrylate and      2ethylhexyl methacrylate (23.1/21.5/18.5/18.0/9.2/9.2 weight ratio); 60%      solids in butyl acetate.                                                 

EXAMPLE 11

This example describes the preparation of a two-component curable primercoating composition containing the acetoacetylated polysiloxane tetrolof Example 7 in accordance with the present invention. The pre-blendedcrosslinker component which contains the acetoacetylated polysiloxanetetrol was combined under agitation with the pigmented component, whichis commercially available as NCP-270 from PPG Industries, Inc., justprior to application to a metal substrate.

    ______________________________________                                                           Formula Weight                                                                            Solid Weight                                     INGREDIENT (grams) (grams)                                                  ______________________________________                                        PIGMENTED COMPONENT:                                                            Methyl isobutyl ketone (MIBK) 10.9 --                                         Butyl acetate 11.9 --                                                         Xylene 6.9 --                                                                 Novalac ketimine resin (in MIBK) as in 17.6 14.5                              Example 10                                                                    Acrylic grind resin (in butyl acetate) 2.8 1.7                                as in Example 10                                                              Dysperbyk 110 1.8 .9                                                          MPA2000T polyethylene wax .9 .2                                               Talc 32.1 32.1                                                                Bentone SD-2 1.6 1.6                                                          Titanium dioxide 13.0 13.0                                                    Barium sulfate 14.5 14.5                                                      Silica .4 .4                                                                  Zinc phosphate 25.7 25.7                                                      Iron oxide 2.7 2.7                                                            Carbon black .5 .5                                                            Butyl acetate 3.5 --                                                          Ketimine resin (in MIBK) as in 10.9 10.2                                      Example 10                                                                    Subtotal 157.7 118.0                                                          CROSSLINKER COMPONENT:                                                        Acetone 6.8 --                                                                Methyl amyl ketone 3.8 --                                                     Xylene 3.5 --                                                                 Polyester acetoacetate resin.sup.1 16.4 16.4                                  Siloxane acetoacetate of Example 7 6.8 6.8                                    Bpoxy silane as in Example 10 2.5 2.5                                         Diacrylate resin as in Example 10 2.5 2.5                                     Isostearic acid .1 .1                                                         SUBTOTAL 42.4 28.3                                                            Total 200.1 146.3                                                           ______________________________________                                         .sup.1 Acetoacetylated polyester made from neopentyl glycol/trimethylol       propane/ethylene glycol/cyclohexyl dimethanol/isophthalic anhydride,          1,4cyclohexyl dicarboxylic acid/tertiary butyl acetoacetate                   (2.4/16.7/2.9/3.3/7.7/8.0/59.0 weight ratio).                            

COMPARATIVE EXAMPLE 12

By way of comparison, this example describes the preparation of a twocomponent curable primer coating composition which contains in thecrosslinker component an acetoacetate functional polyester only, with noacetoacetate functional siloxane. The pre-blended crosslinker component,which contains the acetoacetylated polyester, and is commerciallyavailable as NCX 275 from PPG Industries, Inc. is combined underagitation with the pigmented component which is commercially availableas NCP-270 from PPG Industries, Inc. just prior to application to ametal substrate.

    ______________________________________                                                           Formula Weight                                                                            Solid Weight                                     INGREDIENT (grams) (grams)                                                  ______________________________________                                        PIGMENTED COMPONENT:                                                            Methyl isobutyl ketone (MIBK) 21.5 --                                         Butyl acetate 23.5 --                                                         Xylene 13.7 --                                                                Novalac ketimine resin (in MIBK) as in 35.0 28.9                              Example 10                                                                    Acrylic grind resin (in BuAcetate) as in 5.5 3.3                              Example 10                                                                    Dysperbyk 110 3.6 1.8                                                         MPA2000T polyethylene wax 1.7 .34                                             Talc 63.7 63.7                                                                Bentone SD-2 3.2 3.2                                                          Titanium dioxide 25.8 25.8                                                    Barium sulfate 28.7 28.7                                                      Silica .8 .8                                                                  Zinc phosphate 50.9 50.9                                                      Iron oxide 5.3 5.3                                                            Carbon black .9 .9                                                            Butyl acetate 7.0 --                                                          Ketimine resin (in MIBK) as in 21.7 20.1                                      Example 10                                                                    Subtotal 311.6 233.7                                                          CROSSLINKER COMPONENT:                                                        Acetone 11.1 --                                                               Methyl amyl ketone 6.3 --                                                     Xylene 5.8 --                                                                 Polyester acetoacetate resin as in 38.0 38.0                                  Example 10                                                                    Epoxy silane as in Example 10 4.1 4.1                                         Diacrylate resin as in Example 10 4.1 4.1                                     Isostearic acid .1 .1                                                         Subtotal 69.5 46.3                                                            Total 381.0 280.0                                                           ______________________________________                                    

Prior to coating, test panels of various metal substrates were preparedby mechanically abrading the surface with a machine sander and cleaningthe panel of sanding residue. Each of the primer coating compositionsfrom the above Example 10 and Comparative Example 12 were spray appliedusing conventional spray equipment to a variety of metal substrate testpanels and allowed to cure at ambient conditions for two hours. Abasecoat/clearcoat system, DBC-9700/DCU-2020, commercially availablefrom PPG Industries, Inc. was spray applied using conventional sprayequipment and allowed to cure at ambient conditions for one week. Themultilayer coating system was tested for adhesion under variousconditions.

Each of the primer coating compositions from the above Example 11 andComparative Example 12 were spray applied using conventional sprayequipment to test panels of cold rolled steel and electrogalvanizedsteel substrate which had been mechanically abraded and cleaned of allsanding residue. The primer coatings were allowed to cure at ambientconditions for two hours. A commercial topcoat, DCC-9300, available fromPPG Industries, Inc. was spray applied using conventional sprayequipment and allowed to cure at ambient conditions for one week. Themultilayer coating system was tested for adhesion under variousconditions.

These formulations were examined for adhesion to a variety of substratesvia ASTM D-3359. The results are reported on a scale of 0-5 with a 5representing 100% adhesion and a 0 representing greater than 65% loss ofadhesion. A rating of 4 represents less than 5% adhesion loss, 3represents an adhesion loss of 5-15%, a 2 represents an adhesion loss of15-35% and 1 represents an adhesion loss of 35-65%. Adhesion was alsodetermined after humidity resistance testing. Humidity resistance isperformed by placing the cured panels in a cabinet maintained at 100° F.and 100% relative humidity for a total of 96 hours. The panels are thenremoved and examined for adhesion immediately and again after 4 hoursrecovery at room temperature and humidity. Test results for Example 10and Comparative Example 12 are summarized in the following TABLE 1. Theresults for Example 11 and Comparative Example 12 are summarized in thefollowing TABLE 2.

                                      TABLE 1                                     __________________________________________________________________________    COATING           ADH.                                                                              ADH.                                                                              ADH.                                                                              ADH.                                                                              HUMIDITY                                      FORMULATION SUBSTRATE 24 hrs 7 days Hum. Rec. COMMENTS                      __________________________________________________________________________    Example 10                                                                            aluminum  5   5   4   5   good                                          Example 12 aluminum 5 5 1 3 good                                              (Comparative)                                                                 Example 10 cold rolled steel 5 5 5 5 good                                     Example 12 cold rolled steel 5 5 1 5 good                                     (Comparative)                                                                 Example 10 electrogalvanized steel 5 5 4 5 good                               Example 12 electrogalvanized steel 0 0 0 0 microblisters                      (Comparative)                                                                 Example 10 galvanneal steel 5 5 0 5 dense                                           microblisters                                                           Example 12 galvanneal steel 0 0 0 0 small blisters                            (Comparative)                                                               __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________    COATING           ADH.                                                                              ADH.                                                                              ADH.                                                                              ADH.                                                                              HUMIDITY                                      FORMULATION SUBSTRATE 24 hrs. 7 days Hum. Rec. COMMENTS                     __________________________________________________________________________    Example 11                                                                            cold rolled steel                                                                       5   5   4   4   good                                          Example 11 electrogalvanized steel 5 5 3 4 good                               Example 12 cold rolled steel 5 5 2 3 slight blistering                        (comparative)                                                                 Example 12 electrogalvanized steel 5 5 0 2 moderate                           (comparative)      blistering                                               __________________________________________________________________________

EXAMPLE 13

This example describes the preparation of a two-component curable sealercoating composition containing the acetoacetylated polysiloxane tetrolof Example 7 in accordance with the present invention. The pre-blendedcrosslinker component which contains the acetoacetylated polysiloxanetetrol was combined under agitation with the pigmented component justprior to application to a metal substrate.

    ______________________________________                                                           Formula Weight                                                                            Solid Weight                                     INGREDIENT (grams) (grams)                                                  ______________________________________                                        PIGMENTED COMPONENT:                                                            Methyl amyl ketone (MAK) 2.7 --                                               Butyl acetate 2.6 --                                                          Xylene 2.9 --                                                                 Novalac ketimine resin of Example 10 20.4 16.6                                Methyl isobutyl ketone 2.7                                                    MPA 200T polyethylene wax                                                     BENTONE SD-2 0.8 0.8                                                          Silicone additive.sup.1 1.3 0.7                                               Talc 17.9 17.9                                                                Neutral TiO.sub.2 27.6 27.6                                                   Barium sulfate 18.8 18.8                                                      Silica 0.4 0.4                                                                Carbon black 0.2 0.2                                                          Silicone additive.sup.2 0.2 0.1                                               Methyl isobutyl ketone 5.3 --                                                 Ketimine resin in MAK.sup.3 7.1 5.5                                           Methyl amyl ketone 5.7 --                                                     Butyl benzyl phthalate 4.3 4.3                                                Silicone additive.sup.1 0.7 --                                                Subtotal 122.9 93.1                                                           Acetone 11.9 --                                                               Methyl amyl ketone 15.3 --                                                    Xylene 2.8 --                                                                 Siloxane acetoacetate of Example 7 39.4 39.4                                  Adhesion promoter as in Example 10 3.7 3.7                                    Diacrylate resin as in Example 10 3.7 3.7                                     Isostearic acid 0.1 0.1                                                       Subtotal 76.9 46.9                                                            Total 199.8 140.0                                                           ______________________________________                                         .sup.1 Wetting agent commercially available as DISPERBYK 163 from             BYKChemie USA.                                                                .sup.2 Polymethylsiloxane solution commercially available as DC200 from       Dow Corning Corp.                                                             .sup.3 Methylamyl ketone ketimine of diethylene triamine, 78% resin solid     in methylamyl ketone.                                                    

COMPARATIVE EXAMPLE 14

By way of comparison, this example describes the preparation of a twocomponent curable sealer coating composition which contains in thecrosslinker component an acetoacetate functional polyester only, with noacetoacetate functional siloxane. The pre-blended crosslinker component,which contains the acetoacetate functional polyester, was combined underagitation with the pigmented component just prior to application to ametal substrate.

    ______________________________________                                                           Formula Weight                                                                            Solid Weight                                     INGREDIENT (grams) (grams)                                                  ______________________________________                                        PIGMENTED COMPONENT:                                                            Methyl amyl ketone 2.7 --                                                     Butyl acetate 2.6 --                                                          Xylene 2.9 --                                                                 Novalac ketimine resin as in 20.4 16.6                                        Example 10                                                                    Methyl isobutyl ketone 2.7                                                    Polyethylene wax as in Example 13                                             Anti-settling agent 0.8 0.8                                                   Silicone additive as in Example 13 1.3 0.7                                    Talc 17.9 17.9                                                                Neutral TiO.sub.2 27.6 27.6                                                   Barium sulfate 18.8 18.8                                                      Silica 0.4 0.4                                                                Carbon black 0.2 0.2                                                          Silicone additive DC 200 0.2 0.1                                              Methyl isobutyl ketone 5.3 --                                                 Ketimine resin in MAK as in 7.1 5.5                                           Example 13                                                                    Methyl amyl ketone 5.7 --                                                     Butyl benzyl phthalate 4.3 4.3                                                Silicone additive DISPERBYK 0.7 --                                            Subtotal 122.9 93.1                                                           Acetone 11.9 --                                                               Methyl amyl ketone 15.3 --                                                    Xylene 2.8 --                                                                 Polyester acetoacetate as in Example 11 39.4 39.4                             Adhesion promoter as in Example 13 3.7 3.7                                    Diacrylate resin as in Example 13 3.7 3.7                                     Isostearic acid 0.1 0.1                                                       Subtotal 76.9 46.9                                                            Total 199.8 140.0                                                           ______________________________________                                    

Test panels were prepared by hand sanding APR24711 test panels suppliedby ACT Laboratories, Inc. with 360 grit paper to remove contaminants andcleaning to remove sanding residue. The sealer coating formulations ofExample 13 and Comparative Example 14 were spray applied to preparedtest panels using conventional spray equipment and allowed to cure atambient conditions for 4 hours. A commercial basecoat/clearcoat system,DBU-3822/DCU-2001 available from PPG Industries, Inc., was applied tothe cured sealers and allowed to cure at ambient conditions for oneweek. The multilayer coating systems were then tested for chipresistance by impacting the coated panels with 3 mm steel shot andvarying velocities at -22° C. Results are reported as the average areaof coating which exhibits failure caused by impacts at each of threeimpact speeds. Chip resistance test results are reported for sealercoatings of Example 13 and Comparative Example 14 in the following TABLE3.

                  TABLE 3                                                         ______________________________________                                        SPEED                   AVG. AREA DAMAGED                                       OF AVG. AREA DAMAGED EXAMPLE 14                                               IMPACT EXAMPLE 13 (COMPARATIVE)                                             ______________________________________                                        55 mph  13.7 mm.sup.2   46.3 mm.sup.2                                           75 mph 25.4 mm.sup.2 63.6 mm.sup.2                                            95 mph 33.3 mm.sup.2 79.0 mm.sup.2                                          ______________________________________                                    

What is claimed is:
 1. A curable coating composition comprising:(a) a functional polysiloxane having the following general structural formula: ##STR13## wherein R^(a) is an acetoacetate functional group and a portion of the groups represented by R^(a) contains at least two groups having the general structure: ##STR14## the R groups are selected from the group consisting of H, OH and monovalent hydrocarbon groups connected to the silicon atoms, m is at least one; m' is 0 to 50, and n is 0 to 50; and (b) a polyamine or a blocked polyamine.
 2. The curable coating composition of claim 1 wherein the group represented by R^(a) contains a group having the general structure: ##STR15## where X is O or S.
 3. The curable coating composition as recited in claim 2 wherein a portion of the groups of the functional polysiloxane represented by R^(a) contains a group of the general structure: ##STR16## where L is an organic linking group and x is 2 to
 3. 4. The curable coating composition as recited in claim 3 wherein L is alkylene, oxyalkylene or alkylene aryl.
 5. The curable coating composition of claim 4 wherein L is a C₄ to C₂₀ oxyalkylene group.
 6. The curable coating composition as recited in claim 1 wherein the ratio of m:n is from about 0.1 to 10:1.
 7. The curable coating composition of claim 1 wherein (b) is a polyketimine having the following general structure: ##STR17## where p is 0 to 6; R₃ and R₄ are the same or different and are alkylene, oxyalkylene or alkylene aryl; and R'₅ and R"₅ are independently H or alkyl containing from 2 to 20 carbon atoms, or aryl containing from 3 to 24 carbon atoms and each are substantially inert to the ketimine formation reaction; and R'₅ and R"₅ together can form part of a 3, 4, 5 or 6 membered ring.
 8. The coating composition of claim 1 wherein the polyketimine is the reaction product of a polyepoxide with a ketimine containing a secondary amine group.
 9. The coating composition of claim 8 wherein the polyketimine is essentially free of oxirane functionality, has an average of at least two ketimine groups per molecule and has a weight average molecular weight of from about 1000 to about 50,000.
 10. The coating composition of claim 8 wherein the polyepoxide is a polyglycidyl ether of a polyhydric alcohol.
 11. The coating composition of claim 1 further comprising a polyacrylate functional component.
 12. The curable coating composition of claim 11 wherein the polyacrylate functional component has at least two acrylate groups per molecule and a weight average molecular weight from about one hundred to about 50,000.
 13. The composition as recited in claim 11 wherein the polyacrylate is prepared from the reaction of acrylic or methacrylic acid and a polyol.
 14. The composition of claim 13 wherein the polyol is selected from the group consisting of 1,6 hexanediol, trimethylolpropane, pentaerythritol and ethoxylated bisphenol A.
 15. The composition of claim 11 wherein the polyacrylate is prepared from the reaction of a polyisocyanate with an hydroxyl group containing acrylate or methacrylate monomer. 